Cherry rootstock plant named ‘STO3’

ABSTRACT

A new and distinct cultivar of  Prunus  plant named ‘STO3,’ characterized by its upright plant habit and typical hybrid growth; good adaptation to hot and dry conditions; and as a rootstock, slow vegetative growth imparts uniformity, higher yield and better fertility to the grafted variety as compared to a standard rootstock such as Gisela 5, F12/1 and Mazzard.

Latin name of the genus and species: The Latin name of the genus andspecies of the plant variety disclosed herein is Prunus cerasusL.×P.×schmittii Rehder.

Variety denomination: The inventive cultivar of Prunus cerasusL.×P.×schmittii Rehder disclosed herein has been given the varietaldenomination ‘STO3.’

RELATED APPLICATION INFORMATION

This application claims priority to European Community Plant VarietyApplication No. 2012/2007, filed Sep. 24, 2012; the disclosure of whichis incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinct cultivar of Prunusplant, typically used as a cherry tree rootstock, botanically known as PPrunus cerasus L.×P.×schmittii Rehder, and hereinafter referred to bythe name ‘STO3.’

The new and distinct variety of cherry hybrid tree of the presentinvention was bred as a cross of Prunus cerasus with a Prunus canescenshybrid in Germany in 1989. It has been successfully asexually propagatedby tissue culture. The purpose of breeding program was to find a betteradapted cherry rootstock. The new Prunus plant is better adapted to heatand aridity than other rootstocks with a slow vegetative growth. Thebreeder has succeeded in creating a new cherry rootstock, which has ahigher yield and influences the grafted variety positively in fertility.

SUMMARY OF THE INVENTION

Plants of the new Prunus have not been observed under all possibleenvironmental conditions. The phenotype may vary slightly withvariations in environment such as temperature and light intensitywithout any variance in genotype.

The following traits have been repeatedly observed and are determined tobe the unique characteristics of ‘STO3.’ These characteristics incombination distinguish ‘STO3,’ as a new and distinct cultivar ofPrunus:

-   -   1. Upright plant habit;    -   2. Typical hybrid growth;    -   3. Good adaptation to hot and dry clime conditions;    -   4. As a rootstock, with moderate vegetative growth, it produces        a dwarf tree;    -   5. As a rootstock, imparts uniformity and higher yield to the        grafted variety;    -   6. 40% less vigour compared to Prunus avium seedlings; and    -   7. Absence of suckers.

As used herein, “higher yield” refers to the impact of the rootstock ofthe tree on both vegetative as well as generative growth. Thus, therootstock can affect the generative growth and assist the graftedspecies to achieve greater yield. Therefore, with regard to ‘STO3,’ theyield per tree and crown volume is higher than that of a standardrootstock such as Gisela 5, F12/1 and Mazzard.

Further with ‘STO3’ as the rootstock, the grafted variety can achievebetter fertility (i.e., greater generative growth). That is, use of‘STO3’ as a rootstock results in greater generative growth than in thecase of standard rootstock (Gisela 5, F12/1, Mazzard); the tree producesmore flowers, more fruit, with a greater yield of the same or largerfruit size. In the end greater output is achieved.

The parents of ‘STO3’ are partly a hybrid between Prunus avium andPrunus canescens and partly a Prunus cerasus—wild species (all of whichare unnamed and not patented). The parent (Prunus avium×Prunuscanescens) and the parent Prunus cerasus each have a brownish wood,while the new hybrid (‘STO3’) has a greyish wood with a distinctivelenticel grain. Further, the parent Prunus cerasus has a clearly ovalleaf (broadest in the middle), while the lower third of the ‘STO3’ leafbulges and ends in a very sharp tip.

Plants of the new Prunus also can be compared to plants of Prunus‘Weiroot 720’ (U.S. Plant Pat. No. 22,867, issued Jul. 24, 2012). Inside-by-side comparisons conducted in Kressbronn, Germany, plants of thenew Prunus differed primarily from plants of ‘Weiroot 720’ in thefollowing characteristics:

-   -   1. As a rootstock, plants of the new Prunus have about double        the growth in comparison to plants with ‘Weiroot 720’        rootstocks;    -   2. Plants of the new Prunus have hairy one-year-old shoots,        whereas ‘Weiroot 720’ has a hairless one-year-old shoot;    -   3. Plants of the new Prunus have hairs on the lower surface from        the leaves, whereas ‘Weiroot 720’ does not have any hairs on the        lower surface from the leaves; and    -   4. Due to its typical hybrid growth, plants of the new Prunus        impart higher yield to the scion plant than plants of ‘Weiroot        720.’

‘STO3’ was first asexually propagated in autumn 2001 in Freising,Germany, using tissue culture. Asexual reproduction of Prunus rootstockplant ‘STO3’ by tissue culture since autumn 2001 has shown that theunique features of this new variety are stable and the plant reproducestrue to type in succeeding generations of asexual reproduction.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying photographs illustrate the overall appearance of thenew Prunus plant. These photographs show the colors as true as it isreasonably possible to obtain in colored reproductions of this type.Colors in the photographs may differ slightly from the color valuescited in the detailed botanical description which accurately describethe colors of the new Prunus plant.

FIG. 1 provides a side perspective view of a typical tree of ‘STO3’grown in an outdoor orchard.

FIG. 2 provides a close-up view of leaves of ‘STO3’.

FIG. 3 provides a close-up view of fruits, branches and leaves of‘STO3.’

DETAILED BOTANICAL DESCRIPTION

The aforementioned photographs, following observations and measurementsdescribe plants grown during the summer in Kessbronn, Germany in anoutdoor orchard and under conditions and practices generally used incommercial cherry production. Plants were 11 years old when thephotographs and descriptions were taken. Measurements and numericalvalues represent averages for typical plants and plant parts. The actualmeasurements of any individual plant or plant parts, or any group ofplants or plant parts, of the new Prunus plant may vary from the statedaverage. In the following description, color references are made to TheRoyal Horticultural Society (R.H.S.) Colour Chart, except where generalterms of ordinary dictionary significance are used.

‘STO3’ is generally erect and medium strong in growth. The hybrid growthis typical for the new Prunus plant. After eleven growing seasons inKressbronn, Germany, a height of about 5.6 meters, a width of about 3.5meters and a trunk diameter of about 13 cm were observed for ‘STO3.’ Thegrowth reduction induced by ‘STO3’ allows a highly intensive cherryproduction with dwarf trees.

-   Botanical classification: Prunus cerasus L.×P.×schmittii Rehder    ‘STO3.’-   Parentage: Breeding between Prunus cerasus and a Prunus canescens    hybrid.-   Propagation:    -   -   Type.—By asexual reproduction.        -   Method.—By tissue culture since the autumn of 2001 in a            controlled environment. The process is similar to the            propagation of other cherry rootstock.-   Plant description:    -   -   Plant and growth habit.—Used a rootstock; upright plant            habit; plants are typically grown as a single stem; moderate            vigor.        -   Stem description.—Strength: Strong. Texture: Rough. Color:            Grey brownish RHS 199B.        -   Leaf description, fully developed leaves.—Arrangement:            Alternate; simple. Length: About 5.8 cm to about 7.2 cm.            Width: About 3.5 cm to about 4 cm. Shape: Elliptic to ovate,            moderately elongated. Apex: Acute. Tip: Acuminate. Base:            Obtuse. Margin: Biserrate. Texture, upper surface: Glabrous.            Texture, lower surface: Coarse, pubescent. Color: Fully            developed leaves, upper surface: Close to RHS 136A;            venation, close to RHS 146C. Fully developed leaves, lower            surface: Close to RHS 137C; venation, close to RHS 152D.        -   Petiole description.—Length: About 1 cm to about 1.6 cm.            Diameter: About 0.16 cm. Color, upper surfaces and lower            surfaces: Close to RHS163A.        -   Presence of stipules.—Present. Frequency: Not at every bud.        -   Stipule description.—Length: About 0.6 cm to about 1 cm.            Width: About 0.3 cm. Shape: Triangular, very elongated.            Margin: Erose.-   Flower description:    -   -   Flower type/habit.—3 to 6 flowers single flowers arranged on            compound panicles. Flowers occur in general on one year old            branches.        -   Fragrance.—Weak, pleasant.        -   Natural flowering season.—In April in south Germany, three            days before ‘Weiroot 720’ (U.S. Plant Pat. No. 22,867).        -   Lastingness of entire bloom period.—About 15 days.        -   Lastingness of an individual bloom.—About 8 days.        -   Inflorescence height.—About 4 cm to about 4.6 cm.        -   Inflorescence diameter.—About 5 cm to about 9 cm.        -   Flower diameter.—About 2.4 cm to about 3.1 cm.        -   Flower depth.—About 1.2 cm to about 1.5 cm.        -   Bud length.—6-10 mm.        -   Bud width (bud diameter).—3-5 mm.        -   Bud shape.—Cylindrical, tapering (obtusely pointed) at the            protruding end.        -   Bud colour.—Brown to reddish brown -RHS- 1683A.        -   Petals.—Arrangement: Five petals in a single whorl. Length:            About 1.2 cm to about 1 cm. Width: About 1 cm to about            1.2 cm. Arrangement: Slightly overlapping. Shape: Oblong,            slightly elongated. Apex: Rounded, slightly elongated. Base:            Truncate. Margin: Entire. Texture, upper and lower surfaces:            Smooth, glabrous. Color: When fully opened, upper surface:            Close to RHS 155B. When opening and fully opened, lower            surface: Close to RHS 155B.        -   Sepals.—Arrangement: Five sepals in a single whorl. Length:            About 0.4 cm. Width: About 0.3 cm. Shape: Triangular,            moderately elongated. Apex: Pointed. Base: Truncate. Margin:            Entire. Texture, upper and lower surfaces: Smooth, glabrous.            Color, upper surfaces: Close to RHS 142B. Color, lower            surfaces: Close to RHS 145B.        -   Pedicels.—Length: About 2.3 cm to about 2.6 cm. Diameter:            About 0.1 cm. Angle: About intermediate to semi-prostrate            from the inflorescence stalk. Texture: Smooth, glabrous.            Color: Close to RHS 142A.        -   Peduncle.—Length: About 0.1 cm. Diameter: About 0.2 cm.            Surface: Smooth. Color: Close to RHS 149A.        -   Reproductive organs.—Stamens: Quantity per flower: Numerous.            Filament length: About 5 mm to 12 mm. Filament color: Close            to RHS 155B. Anther length: About 0.3 mm to about 1 mm.            Anther color: Close to RHS 6A. Pollen color: Close to RHS            6D. Pistils: Quantity per flower: One. Pistil length: About            10 mm to about 13 mm. Style length: About 8 mm to about            11 mm. Style color: Close to RHS 150C. Stigma shape: Round.            Stigma color: Close to RHS 149A.        -   Fruit description.—Maturity when described. Date picking:            July in south Germany, varies with climatic conditions:            About the same time as ‘Weiroot 720’ or about three days            later. Size: Small, about 1.3 cm to about 1.6 cm diameter.            Average weight: about 1.5 g, varies slightly with fertility            of the soil, amount of thinning and climatic conditions.            Form: Globose, Slightly flat at the apex. Stem cavity:            Slightly obcordate to flat. Color: RHS 40A.        -   Peduncle description.—Size: Average length about 3.6 cm.            Average diameter about 0.1 cm. Color: RHS 149A.        -   Stone description.—Average length: about 0.8 cm. Average            width: about 0.75 cm. Average thickness: about 0.66 cm.            Form: Nearly globose. Base: Flat. Apex: Rounded. Color: RHS            164C when dry.        -   Fruit use.—Not be used as a dessert fruit.-   Pollination requirements: ‘STO3’ is not self-fertile and requires a    pollinator.-   Temperature tolerance: Plants of the new Prunus have been observed    to tolerate temperatures from about −20° C. to about 40° C. Notably,    under hot and dry climate climatic conditions, ‘STO3’ trees do not    exhibit chlorosis. These trees are very robust in the presence of    substantial variations in temperature (very low temperatures in    winter (−20° C.) and very hot temperatures in summer (+40° C.)) and    such temperature fluctuations have no negative effect on the trees.-   Drought tolerance: Due to a deep root system, the new variety,    ‘STO3,’ is tolerant to drought conditions.

What is claimed is:
 1. A new and distinct cultivar of Prunus cerasusL.×P.×schmittii Rehder plant named ‘STO3,’ substantially as illustratedand described herein.